PIK3CA and breast cancer: Western blot results confirmed the inhibition of BYL719 on PI3K/AKT signaling pathway, showing the suppressed phosphorylation levels of AKT and S6 as well as elevated expression level of apoptotic marker PARP along with increased concentration of BYL719 in two PIK3CA mutated breast cancer cell lines MCF7 and T47D (Figure 1C).